1. Field of Invention
The present invention relates to propylene copolymer compositions and methods for the preparation of propylene copolymer compositions, which preferably include propylene copolymers having particular types of diene units.
2. Description of Related Art
Various processes have been proposed for making propylene copolymer compositions. Such different processes will typically have different variables and parameters, including different monomer compositions, solvents, additives, reaction conditions, catalyst systems, etc. The properties and characteristics of the final product have a great deal to do with the process variables and parameters that are selected, and it has been recognized that small modifications in such variables and parameters can create significant differences in not only the final product, e.g., polymer properties, but also in the effectiveness of the overall process, e.g., catalyst productivity, presence or absence of gel. See, for example, background references that include U.S. Pat. Nos. 5,514,761, 5,635,573, 6,225,432, U.S. application Ser. No. 2002/013440 A1, WO 98/49229 A, WO 00/06621 A, WO 01/46273 A, WO 02/090399 A, WO 02/50145 A, EP 0 667 359 A, EP0718 324 A, EP0 806 436 A, EP0 942 017 A, EP 1 008 607 A, EP 1 195 391 A, JP Abstract 06 025357 A, and Hackman et al., Functional Olefin Copolymers: Uniform Architectures of Propene/7-methyl-1,6-octadiene Copolymers by ATR-FTJR Spectroscopy Control of Monomer Composition, 33 MACROMOLECULES 5, 1524-1529 (2000).
An ongoing need exists for processes that provide propylene copolymers with suitable functionality, good processability and high melt strength, which are desirable for applications such as radiation resistance, paintability, dyeability, functionalization, adhesion, compatibility, thermoforming, foaming, and blow molding. Poor melt strength of polypropylenes shows up as excess sag in sheet extrusion, rapid thinning of walls in parts thermoformod in the melt phase, low draw-down ratios in extrusion coating, poor bubble formation in extrusion foam materials, and relative weakness in large-part blow molding. The polypropylene homopolymer as such is deficient in radiation resistance, adhesion, paintability, compatibility that preclude its use in many end-use applications. Thus, it would be highly desirable to produce a polypropylene having olefinic functionality, enhanced melt strength and commercially valuable processability.
Furthermore, a need exists for a polypropylene copolymer that, when formed in the reactor system, has desirable properties, e.g., branching, without undesirable side-effects, e.g., gel formation; and that after polymerization can be subjected to crosslinking preferably without substantial loss of desirable polymer properties.